We've all heard the saying: practice makes prefect! In other words, acquiring skills takes time and effort. But how exactly does one go about learning a complex subject such as tennis, calculus, or even how to play the violin? An age-old answer is: practice one skill at a time. A beginning pianist might rehearse scales(音阶) before chords(和弦). A young tennis player practices the forehand before the backhand. Learning researchers call this “blocking”， and because it is common and easy to schedule, blocking is dominant in schools, training programs, and other settings.

However another strategy promises improved results. Enter “interleaving”， a largely unheard-of technique that is catching the attention of   cognitive(认知) psychologists and neuroscientists. Blocking involves practicing one skill at a time before the next (for example, “skill A” before “skill B” and so on, forming the pattern “AAABBBCCC”), while in interleaving one mixes practice on several related skills together (forming for example the pattern “ABCABCABC”).

Over the past four decades, a small but growing body of research has found that interleaving often outperforms blocking for a variety of subjects, including sports and category learning. Yet there have been almost no studies of the technique in unplanned, real world settings-until recently. New research in schools finds that interleaving produces dramatic and long-lasting benefits for an essential skill: math. Not only does this finding have the potential to transform how math is taught, it may also change how people learn more generally.

Researches are now working to understand why interleaving produces such impressive results. One important explanation is that it improves the brain's ability to tell apart between concepts. With blocking, once you know what solution to use, or movement to do, the hard part is over. With interleaving, each practice attempt is different from the last, so rote(死记硬背) responses don't work. Instead, your brain must continuously focus on searching for different solutions. That process can improve your ability to learn critical features of skills and concepts, which then better enables you to select and produce the correct response.

A second explanation is that interleaving strengthens memory associations. With blocking, a single strategy，temporarily held in short-term memory, is sufficient. That's not the case with interleaving-the correct solution changes from one practice attempt to the next. As a result, your brain is continually engaged at regaining different responses and bringing them into short-term memory. Repeating that process can strengthen neural connections between different tasks and correct responses, which improves learning.

Both of these accounts imply that increased effort during training, either to discriminate correct responses or to strengthen them, is needed when interleaving is used. This corresponds to a potential drawback of the technique, namely that the learning process often feels more gradual and difficult in the beginning. However, that added effort can have better, longer-lasting results.